Fuel cells in which hydrogen gas is used as an anode fuel and air is used as a cathode oxidant is old in the art. Such fuel cells are generically called hydrogen-air fuel cells and operate to convert the chemical energy of the fuel (hydrogen) into electric energy by galvanic action.
In the recent past, special interest has been given to the use of hydrocarbons as a cheap and plentiful fuel for fuel cells. Due to the low energetic characteristics of hydrocarbons, when put to such use, that interest has, prior to my invention, failed to bring any notable beneficial results.
Automobile manufacturers have been directing great attention and efforts towards developing electric vehicles in order to meet state, federal and global air pollution goals and our dependence on imported fossil fuels, it is causing us to rethink our current means of transportation.
As a result of the above, there is an ongoing search for advanced batteries and/or fuel cells for the purpose of generating electric power for electric vehicles, which are light weight, are inexpensive to make and operate and that will, for example, propel an electric vehicle four to five hundred miles per fueling or charge.
To the above end, some interest has been directed to the use of the current automobile gasoline fuel infrastructure system for fuel cell fuels; and thereafter adding ethanol and methanol to said fuel infrastructure system as soon as practical.
The present invention concerns those fuel cells that use a gas as the fuel or oxidant. Such cells have electrodes which provide gas-electrolyte-electrode interfaces. For good cell performance, the electrolyte should penetrate into the electrode sufficiently to reach the interior surfaces of the electrode and thereby contact the gas in as many places as possible in the presence of a noble metal on the electrically-conducting carbon electrode. The ions being formed by the cell reaction should move freely from the reaction zone to and from the electrolyte separator. In fuel cells, the electrodes and the electrolyte should, in theory, maintain a constant balance value, while the fuel and oxidant react and are spent electrochemically, and the electricity and product of reaction are removed from the cell.
In operation, fuel cell catalytic reaction is dependent upon the effective surface area of contact afforded by the noble metal catalysts on the carbon electrodes. Since platinum or other noble metals are very expensive, it is desirable to achieve the greatest surface area of noble metal per unit of material utilized in the electrodes.
The platinum or noble metal of my invention in the high surface area carbon electrode is incorporated by inorganic gels of platinum or other noble metals mixed into an organic gel of resorcinol and formaldehyde. This invention may use any number of nobel metal catalysts, the most useful of which are cobalt, rhodium, iridium, palladium, platinum, silver, gold, ruthenium, and osmium. The choice of a specific catalyst depends mainly on the intended use for the gas electrode.
In accordance with the teachings of my inventions which are the subject matter, U.S. Pat. No. 4,659,634, entitled Methanol Hydrogen Fuel Cell System and issued Apr. 21, 1987, and U.S. Pat. No. 4,684,581, entitled Hydrogen Diffusion Fuel Cell and issued Aug. 4, 1987, it is apparent that hydrocarbons are readily reformed into hydrogen (H.sub.2) and carbon dioxide (CO.sub.2) gases that can be put to use as fuel. It is easy and economical to produce impure hydrogen-enriched gases by what is commonly called Steam-Hydrocarbon Reforming methods and processes wherein hot vaporous or gaseous mixtures of steam (water) and hydrocarbon are moved into contact with a heated reformer catalyst, such as a porous nickel body in which they react and are reduced to said gases.
The art of making those micro porous materials called aerogels, is old in the art. Aerogels were invented in the 1930s by Samuel S. Kistler. Their manufacture is described in U.S. Pat. No. 2,093,454, issued Sep. 21, 1937 and entitled Method of Producing Aerogels. The manufacture of carbon aerogels is described in U.S. Pat. No. 4,997,804, issued Mar. 5, 1991 and entitled Low Density, ResorcinoI-Formaldehyde Aerogels. The manufacture of Resorcinol-Formaldehyde novolacs fibers is described in U.S. Pat. No. 3,650,102, issued Mar. 21, 1972 and entitled Fibers from Novolacs. The manufacture of carbonized fibers for fuel cell electrodes is described in U.S. Pat. No. 3,960,601, issued Jun. 1, 1976 and entitled Fuel Cell Electrode. The manufacture of carbonized fibers for fuel cell electrodes is described in U.S. Pat. No. 3,972,735, issued Aug. 3, 1976 and entitled Method For Making Electrodes For Electrochemical Cells.
The potential use of carbonized aerogels as carriers of catalysts to afford a high surface area in little space, has been alluded to in the teachings of the prior art, but I am unaware of any teachings of the use of such materials in the art of fuel cells.
The use of electrically conductive catalyzed micro porous carbon electrodes in my present invention, composed of carbonized organic gels of resorcinol and formaldehyde mixed with inorganic gels of platinum or other noble metals, is understood and believed to be a new and a meritorious advance in the fuel cell art.
The possible use of aerogels to establish immense catalyzed surface areas in very little space has been alluded to in the teachings of the prior art, but I am unaware of any teaching of the use of such materials in the art of fuel cells. The use of electrically conductive aerogels for fuel cell electrodes in my present invention is thought to be new in the fuel cell art.